Printed electronics is one of the fastest growing technologies in the world. It makes much more possibilities to kinds of industries such as consumer goods, healthcare, aerospace, electronics, media and transit. It allows electronics to be used in field of it has never been before and improving existing electronic products and electrics. It is specifically a set of printing methods used to create electrical devices on various substrates. Printing typically uses common printing equipment suitable for defining patterns on materials, such as screen printing, flexography, gravure, offset lithography, and inkjet printing. The printed electronics offer an attractive alternative to conventional technologies by enabling creation of large-area, flexible devices at a low cost. There is a plethora of applications for high-conductivity materials with fine-scale features in modern electronics such as solar cell electrodes, flexible displays, radio frequency identification tags, antennas, etc. The printed electronics are expected to facilitate widespread, very low-cost, low-performance electronics for applications such as flexible displays, smart labels, decorative and animated posters, and active clothing that do not require high performance. For the preparation of printed electronics, nearly all industrial printing methods can be employed. Similar to conventional printing, printed electronics apply ink layers one atop another. So, the coherent development of printing methods and ink materials are the field's essential tasks.
Recent attention has focused on flexible substrates as a low-cost, enabling platform for portable, lightweight, and disposable devices. Such devices require conductive electrodes, which, to date, have been deposited by screen printing, sputter coating, inkjet printing, and airbrush spraying. However, these deposition methods involve use of an ink which may not be convenient in fast prototypes due to complicated curing methods and consequently no ink in the present state of art is immediately conductive after writing.
Flexible substrates offer many advantages for printed electronic devices. Not only are flexible substrates widely available and much more convenient, they are lightweight, biodegradable, and can be rolled or folded into three-dimensional (3D) configurations. Functional electronic components, including thermochromic displays, disposable radio frequency identification (RFID) tags, and cellulose-based batteries have recently been produced on flexible substrates. The wide variety of flexible substrates such as polyethylene terephthalate (PET), polyimide (PI), paper substrates etc., and coatings can be exploited to enable specific device architectures. Facile routes to creating devices with inks which are immediately conductive upon writing under ambient conditions could make it possible to fully exploit the potential of flexible printed electronics.
In the present state of art, various technologies are known which produce conductive ink, particularly silver-based conductive inks for writing on a plurality of substrates. However, these inks face numerous technical issues. Firstly, the inks or pastes normally require printing equipment to form patterns and require curing at high temperature to achieve reasonable conductivity for the printed trace. Thus, it is not suitable for a product with writable pen shape to be used for the application in fast prototyping and educational toy industry. Secondly, the drying/curing time for such inks is long and the ink is not immediately conductive upon printing. Thirdly, many such inks contain nanoparticles which require high curing temperature, have much limitation on the products and reduce their large-scale availability. Lastly, the conductive trace formed is hard to be modified after print-out by the conductive inks available in the present art. It is not convenient for electronic engineers doing fast prototyping.